Initial p(A) - 10.0 atm

Initial p(B) - 10.0 atm

Initial p(C) - 0.0 atm

What I have so far:

Since total pressure remains the same the amount of pressure taken away from A and B must be same as the increase in C so:

A + B ==> 2C

Other than this I have no clue on how to get a value for equilibrium pressure, HELP!